There is an emerging consumer market for certain devices that are used as companion products to smartphone devices. Their popularity can be traced, in part, to the variety of features they provide to a user. For example, one such device is a wearable device, such as a ring worn on the user's finger, a necklace, glasses, or a “wristlet” (e.g., a watch or wristband) that is worn around a user's wrist. Typically, such wearable devices may provide different features, such as a logging function that monitors the user's motion and resting activities, and then sends a report on the detected motion and activities to the user's smartphone for storage in memory. Another feature allows the wearable devices to be used as a personal token to automatically gain access to a smartphone that has been locked. Particularly, a wearable device worn by the user may communicate with the user's smartphone, thereby permitting the user to bypass the manual entry of a predetermined unlock sequence associated with the smartphone.
Such features are already present on commercial products. However, a common issue associated with these devices is that they either need a physical interface (e.g., 3.5 mm audio plug, an Universal Serial Bus (USB), etc.), or some sort of wireless “local connectivity” (e.g., BLUETOOTH, WiFi, Near Field Communication (NFC), etc.), in order to transmit data between the devices. Such methods for communicating, however, can be cumbersome. Additionally, these types of communication may be a limiting factor that could constrain new features waiting to be implemented on such devices.
There are existing solutions utilizing such local connectivity technologies such as BLUETOOTH/BLE and WiFi in order to detect a wristlet in close proximity to a smartphone. However, these methods are not able to accurately measure a distance and establish a deterministic distance between the wristlet and the smartphone. Typically, different materials positioned near the wristlet and the smartphone can interfere with (i.e., signal attenuation) and reflect (i.e., signal gain) the wireless communications between the two devices. Similarly, under some extreme conditions, other transmitting devices or signals can also interfere with the communications. Thus, such solutions are not able to provide accurate distance detection making it difficult for a smartphone to determine if a wristlet or other wearable device is or is not within a predetermined, preferably short-range, distance.